1. Technical Field
The present disclosure relates to a method of fabricating a wiring board formed on a support board and a method of fabricating a semiconductor device constituted by mounting a semiconductor chip on the wiring board.
2. Related Art
In recent years, high density formation and thin-sized formation of a semiconductor chip has been promoted in accordance with high speed formation and high integrated formation of a semiconductor device and high density formation/thin-sized formation are requested similarly to a wiring board connected with the semiconductor chip.
In order to deal with high density formation of a wiring of the wiring board and thin-sized formation thereof, in recent years, the main current is constituted by a method of forming a wiring board by a so-to-speak build up method. When a multilayer wiring board is formed by the build up method, the multilayer wiring board is formed as follows.
First, a build up layer comprising an insulating resin layer is formed on a support board (core board) having a pertinent rigidity, a via hole is formed at the build up layer, thereafter, a via plug is formed at the via hole by a plating method and a pattern wiring connected to the via plug is formed. Thereafter, by repeating the steps, a multilayer wiring board can be formed by the build up method.
The build up layer (insulating resin layer) comprises a soft material of, for example, thermosetting epoxy resin or the like and therefore, in order to maintain flatness of the build up layer, there is adopted a method of forming the build up layer on a support board having a pertinent rigidity (For example, See Japanese patent document JP-A-2002-198462).
However, it is requested to further subject the wiring board formed by the build up method to thin-sized formation and therefore, there has been proposed a structure of removing the support board, or a wiring board having a so-to-speak coreless structure.
However, when the wiring board is constituted by the coreless structure, a rigidity of the wiring board is reduced. Therefore, there poses a problem which becomes difficult when after removing the support board or exfoliating the wiring board from the support board, a step of laminating a necessary layer on the wiring board and working the wiring board is provided. An example of the step will be explained as follows.
For example, water absorbing performance of the build up layer is high and in a state of exposing a surface thereof, there is brought about a concern in insulation reliability over a long period of time and it is preferable to cover the surface by a protecting layer of a solder resist layer or the like. However, according to the build up method of the related-art, when the solder resist layer covering the surface of the build up layer formed right above the support board is formed, it is necessary to remove the support board or exfoliate the build up layer from the support board.
In this case, it is necessary to carry the wiring board in the midst of working in which the support board is removed and the rigidity is reduced to pose a problem that a concern of damaging the wiring board is increased. Further, when the solder resist layer is formed at the build up layer after removing the support board, the rigidity is insufficient and therefore, there is a case of posing a problem in flatness of the wiring board.
Therefore, there is a case in which it is difficult to excellently maintain accuracy of working the solder resist layer. The problem of the accuracy of working the solder resist layer becomes significant particularly when a wiring board in correspondence with a high function semiconductor chip in recent years which is subjected to high density/high integrated formation.